<?php

namespace Common;

use Common\Database\DBPDO;

class Database
{

    protected static $conn;

    // 私有构造 单例模式 第一步
    private function __construct()
    {
    }

    // 获取单利模式
    public static function getInstance()
    {
        if (self::$conn == null) {
            self::$conn = new self();
        }
        return self::$conn;
    }


    public function where()
    {
        return $this;
    }

    public function order()
    {
        return $this;
    }

    public function limit()
    {
        return $this;
    }
}
